1. Field of the Invention
The present invention relates to a still picture transmission-display apparatus for speed-changing, transmitting and displaying still picture data.
2. Description of Related Art
FIG. 1 is a block diagram of a still picture transmission-display apparatus of the conventional storage conversion type speed changing system.
At the transmission side of this apparatus are provided an analog/digital (A/D) converter 1 which converts into digital still picture data analog still picture data, such as R.G.B. video signals, obtained by a usual video camera or by a graphic board of personal computers, a frame memory 2 for storing therein digital still picture data corresponding to one picture pane of cathode ray tube (CRT), a write timing generator 3 for generating a sampling clock Cl1 for the A/D converter 1 and a write control signal S1 for the frame memory 2 on the basis of a horizontal synchronizing signal H and a vertical synchronizing signal V, a transmission timing generator 4 for generating a read control signal S2 and a transmission timing signal S3 for the frame memory 2 on the basis of the horizontal and vertical synchronizing signals H and V, and a multiplex transmission unit 5 for multiplex-transmitting the digital still picture data to the receiving side.
At the receiving side connected to the transmission side of such construction through a transmission line 14 are provided a receiving/regenerating unit 6 for receiving and regenerating the digital still picture data transmitted through the transmission line 14, a frame memory 7 for storing therein the digital still picture data corresponding to one picture plane of CRT, a digital/analog (D/A) converter 8 for converting into analog still picture data the digital still picture data read out from the frame memory 7, and a CRT controller 9 for generating a read control signal S4 for the frame memory 7, Sampling clock CL2 for the D/A converter 8, and the horizontal synchronizing signal H and vertical synchronizing signal V to CRT (not shown).
Next, explanation will be given on operation of the apparatus.
At the transmission side, the inputted analog still picture data is converted into digital still picture data by the A/D converter 1 according to the clock CL1 from the generator 3 and the digital still picture data corresponding to one picture plane is written into the frame memory 2 in synchronism with the control signal S2 from the generator 3, wherein the generator 3 generates the clock CL1 and control signal S1 on the basis of the inputted synchronizing signals H and V of analog still picture data, whereby the digital still picture data corresponding to one picture plane is written in the rear time into the frame memory 2 in synchronizing with the synchronizing signals of analog still picture data, the digital still picture data written in the frame memory 2 is read out from the frame memory 2 in synchronism with the control signal S3 from the generator 4, multiplexed according to a protocol at the multiplex transmission unit 5, and sent out to the transmission line 14 in accordance with the timing signal S3 from the generator 4.
A the receiving side, the digital still picture data corresponding to one picture plane transmitted through the transmission line 14 is multiplex-separated and regenerated by the receiving/regenerating unit 6 according to the protocol so as to be written into the frame memory 7 according to a write control signal S5 from the receiving/regenerating unit 6. The digital still picture data in synchronism with the display timing is repeatedly read out from the frame memory 7 according to the control signal S4 from the analog still picture data, for example, R.G.B. video signals, in accordance with clock CL2 from the controller 9 and outputted from the D/A converter 8.
The analog still picture data thus obtained is supplied together with the synchronizing signals H and V to CRT and displayed thereby.
Since the conventional still picture transmission-display apparatus is constructed as above-mentioned, the problem is created in that the still picture data only of one kind of the timing specified by the transmission timing generator 4 can be transmitted.
In addition, in the Japanese patent application Laid-Open No. 54-117622, it is disclosed that an image signal from a television camera different in system is received and the line number in the image signal in one field or one frame thereof is counted, thereby automatically discriminating the image signal system and following thereto the circuit operation. This system, however, can correspond only to an image signal different on the line number and directly inputted from a video camera or the like, so that, when the transmission data adopt various systems, the system cannot directly correspond thereto. Also, the Japanese Patent Application Laid-Open No. 61-194992 disclosed the apparatus which identifies the kind of a usual television signal, a video input signal and an R.G.B. external input signal, so as to automatically switch the mode of television receive. Such apparatus, however, is not applicable directly to the image transmission.